1. Field of the Invention
The present invention relates to an ink composition comprising a disilazane-based compound, a colorant and a solvent, an ink cartridge including the ink composition, and an inkjet recording apparatus including the ink cartridge. More particularly, the invention relates to an ink composition comprising a disilazane-based compound, which can suppress formation of bubbles in an ink cartridge during the operation of an inkjet printer, can rapidly remove bubbles once formed, and can demonstrate stability in an initial ejection performance of the ink by activated ink fluidity, an ink cartridge including the ink composition, and an inkjet recording apparatus including the ink cartridge.
2. Description of the Related Art
Due to the recent demand for colored hard copy prints in the field of image processing, various methods of creating colored hard copy prints are being tried. Examples of such methods include a dye sublimation recording method, a thermal wax transfer recording method, an inkjet recording method, an electrophotography recording method, a thermally processed silver salt recording method, and the like.
In inkjet printing, characters and images are recorded by ejecting ink bubbles onto a recording medium, such as a sheet of paper, from a nozzle in a recording head of an inkjet printer to form a point referred to as a “dot.” Inkjet printing has several advantages compared to other technologies, such as low cost, high print quality, easy formability of color images, and so on.
Accordingly, in recent years there has been the widespread use of inkjet printers that allow simplified, high-quality printing in homes and offices to obtain prints comparable to a silver salt photograph by ink-jet printing.
Inks used in inkjet printing are prepared by dissolving or dispersing a water-soluble dye or pigment in a solvent containing water and an aqueous organic solvent. If necessary, additives, such as a surfactant, or the like, may be added to the resultant product.
In order for liquid inks used in inkjet printing to provide high-quality printing for a sustained time period, the inks are required to have optimized properties such as viscosity, surface tension and density. In addition, the inks must not clog nozzle openings of inkjet printers; must not form precipitates due to heat; and must have excellent print image characteristics, such as excellent water resistance, light resistance, and so on, without changing physical properties of the inks.
In addition, when ink is stored in an inkjet system using a large ink tank for a long period of time, foam can be generated in the ink. In this case, it is necessary to remove the foam by inserting an ink circulation system into a print cartridge, which, however, is quite difficult. Accordingly, it is highly desirable to remove the foam generated in the ink in an easy and efficient manner. Also, there exists a need for suppressing generation of foam in the ink.
Prior art ink compositions are prone to bubble formation due to the presence of a surfactant, and the above-described requirements of ink compositions may not be satisfied.
To overcome these problems with prior art ink compositions, Japanese Patent No. 3,078,184, for example, describes a technique in which a fluorine- or silicon-based polymer is added to an ink composition.
Such a fluorine- or silicon-based polymer, however, has poor solubility in ink, so that it requires an ancillary solvent capable of facilitating dispersion or dissolution. Further, these additives, that is, the ancillary solvent and the fluorine- or silicon-based polymer, have poor miscibility with water-soluble additive(s) of the basic ink, and layer separation and hardening of ink may readily occur when they are used in the ink composition. When ink is left for a long period without use, the silicon-based polymer of the surfactant in the ink accelerates drying of the ink in air. Once the ink is dried, the viscosity of the ink is rapidly increased, which causes nozzle clogging due to hardening of the ink on a nozzle surface of a printhead.
Unfortunately, no ink compositions have, to date, proven to be very satisfactory in suppressing formation of bubbles in an ink cartridge, rapidly removing bubbles once formed and demonstrating stability in an initial ejection performance of the ink.